The present invention concerns more particularly a lighting headlamp for a motor vehicle, comprising a light source, a reflector of the elliptical type, a first focus of which is arranged in the vicinity of the source and a second focus of which is arranged in the vicinity of the focal plane of a convergent lens, and a movable mask which is mounted so as to pivot, with respect to a fixed mounting, about an overall transverse axis, and which is capable of occupying an angular occultation position, in which it is arranged substantially vertically in the vicinity of the focal plane of the lens so as to form a cutoff in the light beam produced by the headlamp, and a retracted angular position, a spring forcing the movable mask into its occultation position.
The documents DE-A-38 06 658 and FR-A-2.796.449 disclose such a type of headlamp.
In the document FR-A-2.796.449 for example, an electromagnet acts on the mask by means of a control rod, so as to cause the pivoting of the mask about a transverse axis, with respect to its mounting, from its angular occultation position to its retracted angular position.
The mask is returned elastically to its occultation position by means of a spring and by the effect of a counterweight arranged in a portion of the mask situated under its transverse axis of pivot.
The occultation position is defined by abutment surfaces of the mask which come into axial contact against associated bearing surfaces of the mounting.
As the headlamp is provided to be used in a motor vehicle, it must be in a position to withstand the thermal and mechanical stresses specific to such a use.
However, it has been noted that, under certain vibration frequencies, the return force of the spring is not sufficient to keep the mask in the occultation position, by contact against the bearing surfaces. The mask then tends to move away from the bearing surfaces, allowing passage of the light rays which are emitted by the headlamp above the cutoff and which therefore cause dazzle for the drivers of vehicles travelling in the opposite direction.
The invention aims in particular to remedy this drawback.